Recent published observations have suggested that some patients with Hodgkin's disease may have been close personal contacts with others who subsequently developed the disease. The BCRC investigation was instituted to assess the possible relevance of interpersonal contact in the epidemiology of both leukemia and lymphoma. Following initial evaluations which suggested a high frequency of personal interactions among patients prior to diagnosis, two separate areas were then chosen for case-control evaluation of social linkages. In one of the two areas, the cases had significantly more close personal associations that expected thus supporting, in part, the previous observations of social linkages between patients.